Abstract: Effects of exogenous silicon on spikelet fertility of hybrid rice were investigated  at natural high and normal temperatures during anthesis under field conditions with two hybrids, hightemperature sensitive Jinyou 63  and   hightemperature tolerant Shanyou 63 as material. The exogenous silicon via fertilizer application, in the form of sodium silicon (Na2SiO3·9H2O), was consecutively spayed for  three times at jointing stage at four concentrations,  0 mmol/L (TCK), 1.25 mmol/L(T1.25 ), 2.50 mmol/L (T2.50), and 3.75 mmol/L(T3.75 ). Varietal responses in terms of pollination properties, anther dehiscence and spikelet pollination  rate were examined to establish a feasible screening scheme of the most appropriate sodium silicate application level in rice management practices. Results showed that, sodium silicate applications at the concentration of 1.25 mmol/L, 2.50 mmol/L or 3.75 mmol/L under high temperature in field environments effectively increased the germinated pollen number  per stigma by 16.9% and 39.6% for the heatsensitive Jinyou 63 and heattolerant Shanyou 63, respectively. The number of   pollen grains per stigma increased by 34%  and 305%,  respectively.  The   pollen  germination  rate   rose by 11.3 and 7.0 percentage points, respectively; the percentage of florets with more than 10 germinated pollen grains was increased by 9.3  and 27.6 percentage points,  respectively; while the percentage of florets with fewer than 20  pollen grains  was reduced by 18.8  and 8.1 percentage points,  respectively. Application of the silicon fertilizer also increased anther basal dehiscence width by relative values of 19.0% and 10.3%, respectively, while it improved spikelet pollination rate by absolute values of 10.6 and 4.7 percentage points in the sensitive and tolerant hybrids, respectively. These results showed that the effect of silicon in alleviating fertility reduction may be mainly  attributed to  the pollen quality improvement, but not the pollen quantity or the anther dehiscence. Exogenous silicon   was more effective for hightemperature sensitive  combination  than that for the tolerant and the most effective dosage was at the concentration of 2.50 mmol/L.

Key words: exogenous silicon, high temperature, hybrid rice, seed setting

摘要： 选用硅酸钠（Na2SiO3·9H2O）为硅源，于大田条件下对耐热性不同的2个杂交水稻组合在拔节期连续3次喷施4个浓度水平（TCK, 0 mmol/L; T1.25， 1.25 mmol/L; T2.50， 2.50 mmol/L; T3.75， 3.75 mmol/L）的外源硅，研究施硅对花期自然高温和自然常温下杂交水稻柱头授粉性能、花药开裂性能和受精率的影响，并筛选适宜浓度的硅酸钠施用方案。结果表明，在田间高温条件下，与TCK相比，施硅处理（T1.25、T2.50和T375）使热敏感组合金优63和耐热组合汕优63的颖花受精率分别提高10.6和4.7百分点（绝对值）；花药基部开裂宽度分别增加190%和103%（相对值）；每柱头花粉萌发数增加169%和396%； 授粉总数分别增加34%和305%；花粉萌发率上升113和70百分点；  花粉萌发数大于10粒的小花的占比上升93和276百分点；花粉总数小于20粒的小花占比下降188和81百分点（相对值）。经对两个组合在常温和高温下施硅的花药发育及授粉特性的解析，初步认为外源硅对水稻授粉性能有综合提高作用，但比较而言，其作用可能主要与提高花粉发育质量有关，而提高授粉总数和改善花药裂药性能也有一定的辅助作用。此外，外源硅施用对高温敏感组合效果更佳，其适宜的喷施浓度为2.50 mmol/L。

关键词: 外源硅, 高温, 杂交水稻, 结实